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Organic Chemistry 1 > Exam 3 > Flashcards

Exam 3 Flashcards

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1
Q

Regiocontrol

A

The ability to control where a functional group adds to a compound.

Regiocontrol ≈ Regiospecificity

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2
Q

Nucleophilic Acid

A

An acid whose conjugate base is a strong nucleophile.

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3
Q

Non-Nucleophilic Acid

A

An acid whose conjugate acid is a weak nucleophile.

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4
Q

William Ether Synthesis

A

An SN2 mechanism for synthesizing an ether in which an alkoxide serves as the nucleophile.

RO– = Alkoxide

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5
Q

Examples of Nucleophilic Acids

A
  • HCl (Hydrochloric Acid)
  • HBr (Hydrobromic Acid)
  • HI (Hydroiodic Acid)
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6
Q

Examples of Non-Nucleophilic Acids

A
  • HNO3 (Nitric Acid)
  • H2SO4 (Sulfuric Acid)
  • H3PO4 (Phosphoric Acid)
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7
Q

Why is the conjugate base of a non-nucleophilic acid a poor nucleophile?

A

The conjugate base is resonance stabilized.

The negative charge of the conjugate base is delocalized about the compound by way of resonance.

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8
Q

Oxacycloalkane Formation Kinetics

A

K3 > K5 > K6 > > > K4 > > > K7 > K8

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9
Q

Why does oxacyclopropane form extremely quickly?

A

The proximity of the nucleophilic Oxygen and the electrophilic Carbon compensate for the tremendous ring strain of the three-membered ring.

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10
Q

Why do oxacyclopentane and oxacyclohexane form quickly?

A

The compounds experience minimal ring strain at their bonds, which compensates for the distance between the nucleophilic Oxygen and the electrophilic Carbon.

Oxacyclohexane has zero ring strain due to having bonds with the ideal 109.5° angle.

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11
Q

Why does oxacyclobutane form slowly?

A

The distance between the nucleophilic Oxygen and the electrophilic Carbon does NOT compensate for the great ring strain of the four-membered ring.

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12
Q

Why do oxacycloheptane and oxacyclooctane form extremely slowly?

A

The nucleophilic Oxygen and the electrophilic Carbon are at a great distance from one another, which adds to the instability caused by ring strain within the compounds.

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13
Q

Why do oxacyclopropanes frequently undergo ring-opening reactions?

A

Ring-openings reactions relieve the great ring strain of these compounds.

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14
Q

Nucleophilic Attack on Oxacyclopropane

A

Stereospecific Reaction

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15
Q

Stereospecific Reaction

A

A reaction in which a unique stereoisomer forms a unique stereochemical product.

The cis-configuration and the trans-configuration of a compound will yield different stereochemical products

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16
Q

Regiospecific

A

A reaction in which the addition of a functional group to a compound can only occur at a specific region of the compound.

Regiospecificity ≈ Regiocontrol

17
Q

Why does reacting an alcohol with a non-nucleophilic acid result in an E1 mechanism?

A

The conjugate base of a non-nucleophilic acid is an extremely poor nucleophile since it is resonance-stabilized. A substitution reaction is not possible due to the poor nucleophilicity of the non-nucleophilic base, so an elimination mechanism must be favored.

The non-nucleophilic conjugate base is a weak base, so it cannot perform an E2 reaction.

18
Q

Why does reacting an alcohol with a non-nucleophilic acid create an internal alkene?

A

Formation of an internal alkene is favored because the most stable intermediate and the most stable resultant compound are created.

  • Hyperconjugation causes the internal alkene intermediate to be the most stable carbocation.
  • The internal alkene is most stable due to sp2–sp3 bonding character.
19
Q

Thermodynamic Favorability of Internal Alkene over Terminal Alkene

A

The internal alkene results is more sp2–sp3 carbon bonding than the terminal alkene.

20
Q

Electronic Favorability of Internal Alkene over Terminal Alkene

A

The internal alkene intermediate has a higher number of electron-donating groups than the terminal alkene.

A higher number of electron-donating groups results in greater hyperconjugation stabilization.

21
Q

Internal Alkene Product

A

Zaitsev Product

22
Q

Terminal Alkene Product

A

Hoffman Product

23
Q

How can the Hoffman product be favored over the Zaitsev product during elimination?

A

Using a hindered base for the elimination mechanism restricts the accessibility of hydrogen atoms bonded to internal carbons.

24
Q

Why do alkene addition reactions occur despite being antientropic?

A

During addition of an alkene, one π bond (from the substrate) and one σ bond (from the reagent) are broken and two σ bonds are formed (in the product).

The thermodynamic benefit of σ-bond formation exceeds the entropic loss of the addition reaction.

25
Q

7 Mechanisms for Alcohol Synthesis

A
26
Q

Alcohol Synthesis via SN2

A
27
Q

Alcohol Synthesis via SN1

A
28
Q

Alcohol Synthesis via Reduction

A
29
Q

Alcohol Synthesis from Oxacycloalkane

A
30
Q

What is the driving force of nucleophilic attack of an oxacyclopropane?

A

Relief of ring strain that occurs as the oxacyclopropane ring-opens

31
Q

Vicinal Compound

A

Compound containing a functional group bonded to adjacent carbon atoms.

32
Q

Geminal Compound

A

Compound containing a functional group bonded bonded twice to the same carbon atom.

33
Q

Vic-Diol

A

Alcohol compound containing hydroxyl groups bonded to adjacent carbon atoms.

34
Q

Gem-Diol

A

Alcohol compound containing two hydroxyl groups bonded to the same carbon atom.

35
Q

SN2 Synthesis of Vic-Diol

A

1) Attack an oxacycloalkane with a strong nucleophile at the least hindered carbon of the cyclic ring (i.e. the nucleophile attacks the least hindered C—O bond).
2) Protonate the oxide ion with a polar-protic solvent/reagent to form a second alcohol group.

This synthesis mechanism yields a trans vic-diol.

36
Q

Mechanisms for Vic-Diol Synthesis

A
  • SN2 Synthesis from Epoxide (Trans)
  • Osmium Tetroxide Synthesis from Alkene (Cis)
37
Q

Why is 2-butene more stable than 1-butene?

A
  • The greater inductive-donating (i.e. hyperconjugation) experienced by 2-butene stabilizes the electron-dense double bond.
  • The Zaitsev intermediate (i.e. carbocation is placed on the most substituted carbon) is created during synthesis of 2-butene.

Organic Chemistry 1 (8 decks)

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